You can put a "1" in r5c7. The "1" in the bottom center 3x3 box can only fit in row 7, and this implies that the "1" in the bottom right 3x3 box must go in column 8, leaving r5c7 as the only cell where a "1" can fit in the middle right 3x3 box. dcb

i think you can start with the 4th column, put 7 below 4 and 8 since you need 6,7, or 9 to fill the column. however, you can't have 7 in the 4th or 5th position because 7 is already there for the center block.